Surface plate and method of making same



June 1948. w. s'. POTTER .SURFACE PLATE AND METHOD OF MAKING SAME Filed Dec. 21, 1943 2 Sheets-Sheet 2 iatented June 22, 1948 N l TE D S TAT E S N T O F FI'CE William S. Potter, Edgewood, Pa.

Application December 21, 1943; SerialNo. 515,141

"l Ciaims.

.11 This invention relates to surface or gauge plates such as are in general use in tool and die shopsfor the purpose of laying out work, inspectingan'd checking the accuracy of work pieces,

and also to'an improved method of mounting a surface plate in a supporting structure and providing said plate'with-aworking surface having certain practically desirable characteristics.

The present application constitutes a continuation-in-part of my pending application for paten'tSerial NO."406,733, filed August 13, 1941 which is nowabandoned.

The use of cast iron surface plates for the above purpose has been a customary practice in the-art'formany years. The working surface of the plate-is machined and lapped to produce a trueysmooth finish so that all points on such surface will, with a maximum degree of accuracy, lie in a common-plane. However, after casting such-plates they mustbe aged for a long -period-'to--'msure against warping and require considerable manual work before lapping. It is a common occurrence in the use of cast iron plates, that,- clue to accident or carelessness, a heavy object will be droppedon thesurface and said surface dented or scratched, resulting in the formation of a "burr or elevation of themetal adjacent to the dent or scratch which destroys accurately finished working or testing surface of such'character-thatthe work piece or gauge block will not wring or stick thereto and which is capable of temporarily retaining thereon markings made by a pencil,-or-other writing or drawdug-instrument.

I also provide a novelsupporting structure for the'glass surface'plate and a simple and easily executed method of assembling said plate in fixed relation to the supporting structure; whereby possible flexure or chipping of the glass due to changes in the supporting casting caused by warpage isavoided. Preferably, internal molecu- *lar strains in the glass are first removed by annealingandafter mounting the glass plate in thesupporting structure rtherefor, it is then g-round by .a suitable type of grinder, preferably-employinggrit segments of. siliconcarbicle, of the vitrified-bondtype of coarse and fine grit, and of different grades. It has :been found'that the grinding operation produces a ground surfaceavhich istr-uly flat within a toleranceilimit of 10003, more or less. Such a surface also possesses the practical advantages of enablingxthe work-piece or gauge :block tobe easily :removed therefrom; providing a marking surface :upon which computationsuor drawings may be made; ands theeasy erasureof such markings and cleansing of the platesuriace of oil,.grease. or dirt.

In addition to the above enumerated objects of the invention, it willv be evident from .theiollowing-detailed :clescription that I have devised a glass surface-plate which will be highlyaccurate in iusezandmayzbe economically :maintainBd in proper working:=condition.

Wi'thzI'the. foregoi-ng and other: objects in view the invention consists inxt-he improved surface plate and in the method of assembling the; same .iniasupporting structure, as beuhereinafter more fully. zdescr'ibed, illustrated the; accom- :panying drawing and subsequently incorporated in the sub-joined claims.

Referringanowlto the; drawing, wherein-I have disclosed one *preferred structural embodiment ofumy invention -and in which similar reference characters designate corresponding parts throughout the several views:

figure-'1 is a vertical sectional view showing theglass plate as mounted for :usein .its 'supporting structure in accordance awithnmy; new method;

:Eifillll is atop plan view thereof thev protecting :cover being. Y removed;

Figurei3 is a-vertical sectional view illustrating thenpreferred.:m'ethod of-assembling the glass plate in the supporting frame -.or casting;

.nFigure" 4 .is::a .,simi1ar view-showing a. slight modification .of :saidimethod.

"*Figures 5. and .6 are vertical.- sectional, views similar -to-"-Figure 4, illustrating an alternative method of assembling the gauge ..plate ;in its supporting structure; and

Figurei'l-is. a plan View. of the, assembly-shown ini' Figure: 5.

uzR'eferring in greater detail tozthe: drawing, for thespurpose of illustration, Ihave shown awgauge plateslrll,preferably of plate glass, either colored orsun'co-lored. This plate has a uniform thickness which is, desirably, not less than-approxiz mate'ly oneland one-fourth inches and maybe of any predetermined length and width conveniently suitable for a particular purpose or use. In Figure 1 I have shown the plate Ill rigidly locked or supported within a metal frame casting H. In the present instance this supporting frame is of cast iron and comprises a bottom wall f2, upstanding marginal Walls l3 and horizontal flanges M extending outwardly from the upper edges of said marginal walls. Preferably, the frame is provided at each of its corners with short supporting legs IS. The internal dimensions of the frame H are appreciably greater than the dimensions of the gauge plate in. This plate is preferably directly supported upon and locked to the frame by embedding it in a body of gypsum composition material IE or other materials of like characteristics. Such material may be mixed into a fluent mass that has quick-setting properties, and when set provides an underbed of uniform thickness having contact at all points with the lower surface of the plate Ill and immovably supporting said surface throughout the area thereof in uniformly spaced relation from the bottom wall l2 of the supporting frame. The material it also extends upwardly between the lateral edge faces of the plate In and the marginal walls is of the frame H to the sealing ring H, which is preferably putty.

The plate It is set in the bed material l6 with its upper surface I8 accurately positioned in the plane of the upper surf-aces IQ of the frame flanges I4 and heated pliable sulphur 26, which is impervious to oil, grease or water, is then applied over the putty ring While I have found the putty sealing ring and sulphur finishing strip well adapted for the intended purposes, it is contemplated that various other analogous materials may be employed if desired.

With particular reference to Figure 3 of the drawing, one satisfactory method of preparing the glass plate It! and fixedly mounting the same in its supporting frame may be described as follows:

First, the glass plate is annealed to remove internal strains and also to avoid possible flexure or chipping after mounting in the frame due to the transference of mechanical stresses to the glass caused by warpage of the frame casting. The plate It is then arranged in inverted position with its test surface la in contact with the flat surface of a supporting table 2|.

The frame casting H is provided with a plurality of openings 22 through the bottom wall l2 thereof, and the putty sealing ring I1 is applied to'the inner surfaces of the walls l3 and below the upper surfaces of the frame flanges I l, The frame is now also inverted and positioned over the glass plate ill with the sealing ring I! in sealing contact with the lateral edge faces of the plate and the frame flanges [4 in contact with the surface of table 2|.

The gypsum or like composition, in a semiliquid, fluent or miscible condition, is now poured at room temperature through the frame openings 22 to completely fill all space above the sealing ring l'l between the plate In and frame casting l l. This material will quickly set or harden to provide a locking bed for the plate l having substantially uniform density. When in use the plate will thus be properly supported against flexure by the weight of heavy objects placed thereon. The material I6 is heat resistant and non-deformable under such pressures as may be encountered in the use of the gauge plate.

The frame and plate are now turned over and heated sulphur or equivalent finishing material shown at 28 is applied over the ring l1 and completely fills the remaining space between plate H] and frame H.

The surface N3 of plate lb and the upper surface 59 of the metal supporting frame are now trued by a lapping or grinding machine to quickly bring said surface to the required tolerance limit of flatness. The edges of the frame flanges 14 are also trued with respect to each other and the surface it for convenient use in laying out the work. In this grinding operation I have obtained the best, results by the use of silicon carbide grinding segments, of a vitrified bond type, composed of coarse and fine grit and of different grades. By the use of such segments a large size plate can be ground in one and onefourth hours and a small plate in forty minutes, thus giving maximum production with a perfectly finished test surface which has an opaque appearance of ground glass and will receive penoil markings that are readily erased by wiping across them with a finger. This type of surface may also be produced by sand blasting the glass.

The surface plate is now ready for use. The pouring openings 22 in the bottom wall of the frame casting may be closed by suitable plugs, indicated at 23, and a cover 24 provided to [protect the test surface l8 when the plate is not in use.

In Figure 4.- of the drawing I have shown an alternative spacing means for the putty ring II. This may consist of a wedging frame 25, preferably of wood, adapted to be positioned in snug fitting relation around the glass plate I0, and in con-tact with the table 2|, prior to placement of the frame If thereover. The outer surfaces of the frame 25 may have upper inclined portions 25 which are first engaged by the side walls of the metal frame H to force the frame 25 into sealing contact with the edge faces of the plate it. After the material I'B has properly set the frame 25 may be removed and the space between the frame H and plate l0 filled with hot pliable sulphur :as above explained.

In Figures 5, 6 and 7 of the drawings I have shown another method of assembling the glass gauge plate in accurately fixed relation with its supporting structure, which may be preferred to the method first above described.

In this alternative method the base casting or frame H is first machined, the edges of the legs 55 and surfaces l9 of flange M being ground and the edges of flange l4 milled prior to the assembly. The frame is then placed upon the surface 2 l of an accurate surface plate, or the top surface of a metal work bench, known to be fairly true. The putty seal I1 is then applied to the inner surfaces of the frame walls I3.

Wood blocks l-lil are now inserted through the holes or openings 22 in the bottom wall of the frame casting said blocks resting on the surface 2| and protruding through the openings above the upper surface of the bottom wall |2.

By means of a suction cup device, such as is generally employed in handling glass plates, the plate if! is now placed in position upon the blocks 66, in centered relation to the frame casting and with its lateral edgesequidistantly spaced from the frame walls I3. The blocks 3|! are cut to predetermined size so that the surface l8 of the glass plate will be located approximately /a2 of an inch above the surface IQ of the frame flange i l. The openings 22' are so located in the frame wall I? that the support of the glass plate ll) 5?, upon; blocks-Emile; properly: equalized. As in; thetfirstrdescsibed method, thezg-putty seal: l-='l.!'.'is placedrbelownthesurfaces t9; of the framesands tightly:- seals-\the. underlying space. betweem the; mmelwallsil 3 and the opposed ed'gess ofilthe glassplate I0.

An; angle iron;v frame; l 3 in is; than. placed. upon the-1:plate;,-.lil;. the base:.-fiange 32eofissaid=frame beinggofusuflicient width toiextendioutwardlymver the. major" pontiom of the surface. 1 lpfls'ofi thetsupiportin iframc: lit. 'Iihisxbaseflangeshasia plural.- ity-nof spacednopenings 33 therein: =which:-are':posi'-. tioned in registering."relationswithtthevoid 34:; between. the-edgesofithe plate H! and the frame walls l3, above the putty seal ll. Standard 0 clamps 35 arenowapplied' to engage the base flange 32, of. framet II and, the lower; surfaces of flange 14 of supporting frame -l-- l-,,at.(ca0h=1 e" four sides of said frames. The frame 3| is sumciently rigid so that, as the clamp screws are tightened; the frame casting, H is raisedtinma contact with. the flange 32 ofiframe 3|;7andrits surface lsbrought into alignment-with the ,sur-: face; llhofthe glass plate 'Ilhmcomplete assembly willthen be whollysupported relative-to suriacegzl by; the wood blocks,,3 fl.

Eliable sulphur, heated to liquidgform, is now; poi uiedthrough the openings-=t3ninto the void 34 between theglassnlll andframe H. After the sulphur has solidified the clamps 35"and the frame 3i are-removed and the .frame casting 1, With. the: glass. plate. lfiflnowa;innaccurately centered assembled relation therewith, is lifted off the supporting blocks 30 and turned over with the surface l8 of plate ill and frame flange M in contact with the surface 2!. The ypsum or similar composition is then poured through the openings 22 to completely fill all of the remaining space between the glass plate Ill and the supporting frame or casting ll. After the composition material has properly set or solidified, the assembly is then ready for the final grinding operation to true the surface [8 of plate Ill, as above explained. Any slight misalignment which may exist between the surfaces l8 and IQ of the plate It] and frame II, respectively, after the assembly is completed, will be eliminated in the final grinding operation.

Of course, it will be understood that in this alternative method, the gypsum or other composition, the putty ring and sulphur seal serve the same advantageous purposes as in the method of assembly first described herein.

The practical advantage of my new gauge plate will be readily appreciated by those familiar with this art. The method employed in making the plate I0 and mounting the same in its supporting frame or casting assures a truly fiat testing surface for die blocks or work-pieces, and eliminates the necessity of frequently relapping or grinding said surface to remove burrs or projections thereon resulting from scratches or indentations. Molecular strains in the glass and the transmission of mechanical stresses thereto through the supporting structure are also reduced to a minimum. Thus long life and economical maintenance are realized to offset the somewhat greater production cost, in comparison with the standard cast iron surface plate.

The ground testing surface [8 of the glass plate also has the advantage that metal workpieces or die blocks do not stick or wring thereon and can be easily lifted therefrom, thus avoiding scratching of said surface. Further, such a surface has the required structural charac- I: have: herein disclosed .anstructural embodie: ment. ofnmy; invention-tv whiclnhas-gliien high satisfactory service. It; wilhthowevenzber-a a" parent. that as to-z-therseverali dBtaJil's'xaboy 1- described; saidrzstructure -mayi betexemplifieduima val'iousaother alternative fem-uses.

The invention may be embodiedcinnothemspee cific 'forms .without .:departing& from; the spirit .or essential characteristicr thereof. Thea present;-. embodiments: are therefore ;t.c s. be- 'consideredt-inn all; respects as illustrative and: 1 net: restrictiy ,1,. the scope of I theinvention 2bBiI1g1 indicatedpbyl the appended claims rather ,than by the foregoingz, description andall changes which .come within the,- -mea-ning-- v and; ranges of equivalency oft that. claimsiare therefoie. intendedvto: be; embracedsthere-111;.

What is claimed andzdesiredytotbe secunedrby-y United:- States Letters Patent ,isz:

I-n a-methodofmountinga:gaugeplateeinga supporting; frame, the stepswhich comprise; first? arranging the frame 1 on 3;;111'11653 suppcrtingesua face; then supportingthe gauge plateyindependa ently of said frame with its lateral edges in spaced opposed relation to the side walls of the frame and its upper surface in a predetermined plane relative to the upper surface of said frame walls; then sealing the space between said frame walls and the gauge plate adjacent said upper surface of the plate, and finally filling the space between the plate and frame walls below the seal with a pressure resistant, non-deformable material to permanently lock the plate against displacement with respect to the frame.

2. In a method of mounting a gauge plate in a supporting frame the steps which comprise; first arranging the frame on a trued supporting surface; then supporting the gauge plate independently of said frame with its lateral edges in spaced opposed relation to the side walls of the frame; then relatively moving the frame and gauge plate vertically with respect to said supporting surface to dispose the upper surfaces of said plate and frame substantially in a common horizontal plane; and then introducing an initially pliable, solidifiable sealing medium into the space between said frame Walls and the gauge plate.

3. The method of mounting a gauge plate in a supporting frame which comprises, first arranging the frame on a trued supporting surface, then independently supporting the gauge plate in centered relation to the frame and out of contact with bottom and side walls thereof; then relatively moving the frame and gauge plate vertically with respect to said supporting surface to dispose the upper surfaces of said plate and frame substantially in a common horizontal plane; then sealing the space between said surfaces by the introduction of a pliable solidifiable sealing medium between the edge faces of the gauge plate and the side Walls of the frame; and finally introducing between the frame walls and opposed surfaces of the plate an initially plastic composition material to fixedly lock said plate against movement relative to the frame and uniformly support the upper surface area of said plate in said horizontal plane.

4. The method of mounting a glass gauge plate in a supporting frame having a base wall and upstanding marginal walls, which comprises, first positioning the plate within the frame and applying a; sealing strip in continuous sealing contact with the edge surfaces of the plate and the marginal frame walls, and with the testing surface of the plate substantially flush with the upper edges of said walls, and then introducing an initially miscible composition material between said plate and the frame walls to form a substantially uniformly homogeneous pressure resistant locking bed securing said plate against vertical or lateral displacement relative to the sealing strip and frame walls.

5. The method defined in claim 4, wherein said sealing strip is spaced below the testing surface of the glass plate and finally substantially completely filling said space between the plate and frame walls above the sealing strip, with a heated, solidifiable finishing material.

6. In combination with a metal supporting frame having a base and unstanding marginal walls, a glass gauge plate, and means securing said plate in the frame with its bottom and edge surfaces in spaced substantially parallel relation to the base and marginal walls of the frame and its upper surface disposed in a common plane with the upper surfaces of said marginal walls, said securing means comprising a locking bed of composition material between the frame base 8 and said glass plate having portions thereof Dar tially' filling the space between the edge surfaces of the plate and the marginal frame Walls, and additional means hermetically sealing the remaining space between said plate surfaces and REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Kimble Dec. 21, 1920 Weaver June 23, 1925 Hitchcock Aug. 4, 1925 Challet May 21, 1929 Oestnes Dec. 30, 1930 Riech May 21, 1940 Pottinger Dec. 16, 1941 FOREIGN PATENTS Country Date Great Britain 1918 Number Number 

